Lobular carcinoma in situ

Last revised by Daniel J Bell on 21 Dec 2020

Lobular carcinoma in situ (LCIS) represents the next step up from atypical lobular hyperplasia (ALH) along the malignant spectrum of lobular breast carcinoma.

Lobular carcinoma in situ occurs predominantly in premenopausal women with a mean age of 45 years old, approximately 10-15 years younger than the mean age when invasive breast carcinoma occurs.

Like most other lobular breast pathology, lobular carcinoma in situ originates in the terminal ductal lobular unit (TDLU). However, unlike atypical lobular hyperplasia, the malignant cells fill and distend the lobular acini in LCIS. Unlike invasive lobular carcinoma, they leave the basement membrane intact. They do not express E-cadherin.

Lobular carcinoma in situ is usually incidentally-identified histologically in breast tissue biopsied for other reasons. The exception may be pleomorphic LCIS which is a more aggressive subtype which may be associated with mammographically-detectable calcifications 2.

A substantial percentage of patients with lobular carcinoma in situ have no abnormality on mammography. Non-specific microcalcifications are often the impetus for biopsy in the cases when LCIS is discovered.

Lobular carcinoma in situ is a high-risk marker for the future development of invasive carcinoma. A woman with LCIS has approximately a 15-30% chance of developing an infiltrating ductal or lobular carcinoma in the breast in which the LCIS is discovered or in the contralateral breast.

Approximately 20% (range 18-25%) of cases diagnosed with LCIS at core needle biopsy were upgraded to more invasive cancer pathologies at surgical excision. Therefore when LCIS is discovered on a needle biopsy specimen, an excisional biopsy should be performed.

LCIS was initially first described by F W Foote and F W Stewart in 1941 4

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